The present invention relates to a method of making semiconductor devices, in particular, those that include a dielectric layer that has a hydrophobic surface when initially deposited.
Semiconductor devices include metal layers that are insulated from each other by dielectric layers. As device features shrink, reducing the distance between the metal layers and between metal lines on each layer, capacitance increases. To address this problem, insulating materials that have a relatively low dielectric constant are being used in place of silicon dioxide to form the dielectric layer that separates the metal lines.
Certain materials that may be used to form low k dielectric layers (e.g., carbon doped oxides) are hydrophobic. Their hydrophobic nature renders it difficult to clean their surfaces, and to bond such materials to other layers. In addition, materials that are coated onto a hydrophobic dielectric layer may lack desirable thickness uniformity.
To prevent the hydrophobic character of a carbon doped oxide (or other type of hydrophobic dielectric layer) from adversely impacting a process for making semiconductor devices, a hard mask (e.g., one comprising silicon nitride) may be formed on the dielectric layer""s surface prior to depositing other materials on that layer. Forming such a hard mask on such a dielectric layer increases the cost of the process for making the devices. In addition, using such a hard mask may increase the dielectric constant of the overall insulating layer (i.e., the combination of the hydrophobic dielectric layer and the hard mask), when compared to an insulating layer that includes the dielectric layer only. As an alternative to forming a hard mask on a hydrophobic dielectric layer to address this issue, certain wet chemicals may be used to modify the dielectric layer""s surface chemistry. Because, however, such chemicals are relatively expensive, their use (like adding a hard mask) increases the cost of the process.
Accordingly, there is a need for an improved process for making a semiconductor device that includes a hydrophobic dielectric layer. There is a need for such a process that converts a hydrophobic surface of such a layer to a hydrophilic one in a relatively inexpensive and unobtrusive manner, enabling improved adhesion characteristics and facilitating surface cleaning. The method of the present invention provides such a process.